F The VAC Phi Beta Triode Preamplifier Operation & Maintenance Information Valve Amplification Company Manual issued 02/15/2008
CAUTION THE PREAMPLIFIER AND POWER SUPPLY CONTAIN POTENTIALLY LETHAL VOLTAGES, AND TUBES THAT BECOME HOT IN USE. NEVER OPERATE THE PREAMPLIFIER OR POWER SUPPLY WITH THE COVERS REMOVED. DO NOT REMOVE THE CHASSIS COVERS EXCEPT TO CHANGE TUBES OR LIGHT BULBS. BEFORE OPENING A CHASSIS TO CHANGE TUBES OR LAMPS, DISCONNECT THE POWER SUPPLY FROM AC POWER AND THE AUDIO CHASSIS FROM ALL OTHER COMPONENTS. ALLOW IT TO SIT TURNED OFF FOR 30 MINUTES BEFORE REMOVING THE COVER.
INTRODUCTION The Phi Beta Preamplifier is the world's finest audio preamplifier and an absolutely unique component. Its unusual topology, premium parts, and flexibility make it a pleasure to hear and operate. The line stage is, in effect, a small Class A1 power amplifier, capable of driving loads as low as a few hundred ohms. This is a stark contrast to normal preamplifiers, which claim a low output impedance but completely collapse when asked to deliver current.
INSTALLATION 1) Provide adequate ventilation. 2) Do not operate on carpet or any other surface that might block air flow. 3) The chassis will become warm in normal use. 4) Do not allow the chassis to touch any metal parts, such as the frame of an equipment rack. This might create a parallel ground path that could degrade the sound of your system. 5) Input connection is via single ended RCA jacks or XLR jacks (which can be from balanced or unbalanced sources).
11) Pay close attention to power quality, and be aware that different power cords can alter the sound. The power supply’s backlit meters show variation in power line voltage as reflected to the audio circuitry. 12) 12 volt triggers are provided for control of other audio components.
INPUTS (back panel) Inputs #1, #2, and Cinema may be either unbalanced or balanced. Three connections are possible: 1) Single ended signal on RCA connector. Set adjacent switch to “RCA.” 2) Balanced signal on XLR connector. Set adjacent switch to “BAL.” 3) Single ended signal on XLR connector. Set switch to “BAL.” Alternatively, you may set the switch to “RCA” if and only if the source is “pin 2 hot.” One pair of RCA jacks accommodate the monitor return from a tape deck.
OPERATION Turn the "Volume" control fully counterclockwise. Mute is automatically engaged when switching on the unit. Allow the preamplifier to warm up for a minute before you un-mute the unit; failure to wait can cause a transient to be sent through your power amplifier that might cause damage to your loudspeakers. PLEASE READ THE SECTION ON FRONT PANEL CONTROLS BEFORE USING THE PREAMPLIFIER. As with all high fidelity products, the sound characteristic of the VAC changes somewhat as it warms up.
FRONT PANEL CONTROLS Although most of the front panel controls (Volume, Power, Mute) are self explanatory, VAC has outfitted this unit with several advanced features which bear further description: Power: Turns the unit off and on. Mute: Toggles between the "Mute" and "Operate" condition. When muted, the indicator light is illuminated. Tape: This switch selects between the signal coming from the main selector (light out) or the signal connected to the “TAPE IN” jacks (light on).
Phono: Selects between the MM and MC inputs. Overall phono function is selected with the main Selector switch (phono is one click counterclockwise from “1” or one click clockwise from “6”). PH1 is the MC phono input. It has 64 dB of gain, making it suitable for most low output cartridges. PH2 is the MM input, which provides 44 dB of gain, suitable for use with MM (moving magnet) and many high-output MC (moving coil) cartridges. Optionally, PH2 may be a second MC input.
REMOTE CONTROL The remote control allows for wireless adjustment of POWER, SELECTOR, TAPE MONITOR, CINEMA, MUTE, and VOLUME. The remote wand is powered by two "AAA" batteries. These should be of the alkaline type. You will need to install them in the wand before using the remote. Since batteries can leak, they should be removed from the wand if it is not going to be used for an extended period of time. Be sure to observe the polarity diagram inside th battery compartment.
REPLACEMENT OF LOW LEVEL TUBES Phono tubes are type 12AX7/ECC83; you may wish to use low noise tested tubes. Line stage tubes are type 8416, no substitute types are acceptable. We strongly recommend that you use only tubes specifically selected and tested by VAC for this application. Before replacing tubes, all power must be turned off. Allow 15 minutes for the tubes to cool down and voltages to discharge before removing the top cover. The voltages inside the unit may be lethal in normal operation.
TIPS & ADVICE SECTION A Word About Tubes in General It is true that each brand of tube sounds different in a particular high resolution circuit. This is because no two manufacturers make a tube type in quite the same way, and the central tendencies of the performance parameters will differ slightly with each maker. To emphasize the point, examine the plate structure of any two 6SN7 from different manufacturers will probably find that they may not even the same shape and size.
CARE OF CHASSIS VAC chassis are made from aluminum for superior electromagnetic performance. The main chassis is finished in a durable black powder coat paint, while the fascias are hand rubbed acrylic lacquer. The lacquer should be treated in much the same fashion as a high quality automotive finish. Never apply any dampness or cleaning product to a unit that is plugged in. Do not get cleaning solutions onto or into the tube sockets.
WARRANTY Your equipment is warranted for a period of thirty (30) days from the date of purchase. In addition, if the registration form is received by VAC along with a copy of your sales receipt from an authorized VAC dealer within this thirty days, a service contract will be extended to cover your equipment for two (2) years (tubes excepted).
